This invention relates to a plurality of electronic components each of which has a multi-layered printed circuit board made of a synthetic resin and on which electronic components are mounted in a face-down position. More specifically, this invention relates to an improvement applicable to a structure of electronic components, the structure being appropriate to be employed for a duplexer further employing surface acoustic wave filters.
It is well known that employment of a duplexer employing surface acoustic wave filters is effective to make a mobile data communication means more compact and more efficient.
Two independent prior arts including JPA 5-160664 and JPA 5-167389 are available.
The former one, JPA 5-160664, discloses a structure with which a surface acoustic wave filter is mounted on a substrate, albeit the surface acoustic wave filter is not employed to compose a duplexer in this case. In the structure, metal bumps produced on a surface acoustic wave filter are employed to connect the surface acoustic wave filter and each electrode of the wirings produced on a package, as shown in FIG. 5 of JPA 5-160664. This structure has an advantage in which the amount of impedance is less in comparison with the structure in which bonding wires are employed, and therefore it has an advantage in the characteristics in the technical field of the high frequency electric wave transmission and the other advantage effective for the purpose to make the external dimension thereof compact, as well.
The latter one, JPA 5-167389, discloses a duplexer having two independent surface acoustic wave filters each of which has a pass-band different from each other and of which the rear sides are mounted on a package, as shown in FIG. 5 of JPA 5-167389. Bonding wires are employed to bond the terminals of the surface acoustic wave filter and the terminals of the package, which is a ceramic package in this example. The two surface acoustic wave filters are connected in parallel to each other, and they are connected with a common external signal terminal To of the package (Hereinafter referred to as a common electrode.). This common electrode is connected with a first surface acoustic wave filter via a first wiring branched from the common electrode, and incidentally the common electrode is connected with a second surface acoustic wave filter via a second wiring branched from the common electrode and via an impedance matching circuit (M) connected with the second wiring, as shown in FIG. 1 of JPA 5-167389. The impedance matching circuit is a circuit having a function to prevent a signal to be sent toward the common terminal from the first surface acoustic wave filter, from reaching the second surface acoustic wave filter and having the other function to input a signal which is inputted toward the second surface acoustic wave filter from outside via the common terminal, with a high grade of efficiency.
A duplexer is required to have a package in which two surface acoustic wave filters each of which has a pass-band employable for transmitting a signal and the other pass-band employable for receiving the signal, are mounted thereon and is required to have a good magnitude in heat dissipation and hermetic sealing quality. It is needless to emphasize that it is required to have a good grade of the frequency characteristics.
Since the duplexer of JPA 5-167389 has a structure in which the rear surface of a surface acoustic wave filter is mounted in a ceramic package, it has a good quality regarding heat dissipation, because the ceramic package proper has good characteristics in heat dissipation and the duplexer has a large surface with which the ceramic package contacts the surface acoustic wave filter to readily allow the heat generated in the surface acoustic wave filter to be dissipated outward.
It is clear that cost consciousness is important for an electronic component e.g. a duplexer employing one or more surface acoustic wave filters, such as a duplexer being employable for a compact mobile data communication means.
In this sense, review is required for a ceramic package, which is not inherently less expensive. Further, an electronic component e.g. a duplexer having surface acoustic wave filters mounted on a multi-layered printed circuit board made of bis-maleimide triazine resin et al. and which is covered by a hermetically sealed metal cover, is assumed to be required in the industry.
Accordingly, an object of this invention is to provide a plurality of electronic components having surface acoustic wave filters mounted in a face-down position on a multi-layered organic printed circuit board and having a metal cover covering the surface acoustic wave filters, wherein the metal cover is hermetically sealed with the circuit board and the heat dissipating characteristics are improved.
To achieve the foregoing object, an electronic component in accordance with a first embodiment of this invention comprises:
a multi-layered printed circuit board made of an organic material,
a plurality of electronic components mounted in a face-down position on the multi-layered printed circuit board,
a metal cover for covering the plurality of electronic components remaining a space or a cavity between the bottom surface of the electronic components and the inner surface of the metal cover, the metal cover having a flange surrounding the outskirts of the metal cover to be adhered to the top surface of the multi-layered printed circuit board, and
a heat conductive member packed between the bottom surface of at least one of the plurality of electronic components and the inner surface of the metal cover,
wherein:
the multi-layered printed circuit board has at least one through-hole vertically penetrating the multi-layered printed circuit board at a location corresponding to the flange and being lined by a metal film, and
the multi-layered printed circuit board has a heat conductive layer made of a metal and which is arranged along the rear surface of the multi-layered printed circuit board, the heat conductive layer being connected with the metal film lining the through-hole.
The heat generated in the electronic component in accordance with the first embodiment of this invention is dissipated toward the heat conductive layer via the metal cover and the through-hole. Since the through-hole is arranged to contact the metal flange of the metal cover, the heat is readily dissipated from the metal cover to the heat conductive layer. The heat conductive layer usually contacts an object, e.g. a mother board, on which this electronic component is mounted. These are parameters to make the heat dissipation efficiency better.
The more the quantity of the through-holes is, the better the heat dissipation efficiency is.
It is preferable to bury the internal space of the through-hole with a material having a good grade of heat conductivity, because this is effective to improve the heat dissipation efficiency from the metal cover to the heat conductive layer.
Since an electronic component is required to be compact, it is not easy to allow any area to be employed solely for the purpose of cooling. Therefore, employment of some electrodes as a cooling means as well is a good idea, because this allows some of the areas of an electronic component which areas are not employed for cooling, to be employed for the purpose of cooling. For example, a ground terminal can be preferably employed for a cooling component.
A thermoplastic resin is preferable as a material employable for the heat conductive member, because it is effective to make the stress which is otherwise to be imposed on the electronic component, less.
To achieve the foregoing object, an electronic component in accordance with a second embodiment of this invention comprises:
a multi-layered printed circuit board made of an organic material,
a plurality of electronic components mounted in a face-down position on the multi-layered printed circuit board,
a metal cover for covering the plurality of electronic components remaining a space or a cavity between the bottom surface of the plurality of electronic components and the inner surface of the metal cover, the metal cover having a flange surrounding the outskirts of the metal cover to be adhered to the top surface of the multi-layered printed circuit board, and a heat conductive member packed between the bottom surface of at least one of the plurality of electronic components,
wherein:
the top surface of the multi-layered printed circuit board, which top surface faces the space or the cavity covered by the metal cover, is covered by a metal layer.
In this embodiment, the almost entire internal surface of the space or the cavity confining a plurality of electronic components is covered by a metal layer, resultantly improving the hermetic sealing quality of the space or the cavity confining the surface acoustic wave filters.
The metal layer can be arranged between the layers constituting the multi-layered printed circuit board, in addition to that it is arranged to cover the top surface of the multi-layered printed circuit board.
If some of the through-holes are required to be made to face the space or the cavity in which the surface acoustic wave filters are confined, they are preferably made surface blind through-holes, because a surface blind through-hole is superior in the hermetic sealing quality.
To achieve the foregoing object, an electronic component in accordance with a third embodiment of this invention is a combination of the first and second embodiments.
It is quite natural that the electronic component in accordance with the third embodiment of this invention has both features of the first and second embodiments, to be allowed to enjoy both advantages.
In the case where at least two of the electronic components emit an electromagnetic wave, it is preferable that the heat conductive member is a metal foil bridging the bottom surface of the first surface acoustic wave filter or the transmitting surface acoustic wave filter which generates a larger volume of heat and a selected location of the inner surface of the metal cover, the selected location corresponding to the second surface acoustic wave filter or the receiving surface acoustic wave filter which generates a smaller volume of heat, the metal foil having a U-shaped intermediation of which one end is contacted with one of the edges of the bottom surface of the transmitting surface acoustic wave filter and of which the other end is adhered to the inner surface of the metal cover at a location corresponding to the receiving surface acoustic wave filter, and the U-shaped intermediation having a function to electromagnetically shield the surface acoustic wave filters from each other.
In this case, the metal film has a first function as a heat conductive member and a second function as a shielding member for shielding the electromagnetic waves and a third function to ease stress which otherwise is imposed on the electronic components.
To achieve the foregoing object, an electronic component in accordance with a fourth embodiment of this invention comprises:
a multi-layered printed circuit board further provided with a plurality of insulator layers, each of which is intervened by wirings and/or one or more impedance matching circuits having a strip line structure,
a wiring region arranged on a limited area of the top surface of the multi-layered printed circuit board,
a couple of surface acoustic wave filters bonded in a face-down position on the wiring region,
a plurality of external terminals arranged on the rear surface of the multi-layered printed circuit board, the plurality of external terminals being used for connecting the couple of surface acoustic wave filters,
a couple of conductive layers arranged on the remaining areas of the top and rear surfaces of the multi-layered printed circuit board,
a common terminal selected from the plurality of external terminals,
a first line for connecting the common terminal and one of the surface acoustic wave filters,
a second line for connecting the common terminal and the other one of the surface acoustic wave filters via the impedance matching circuit,
wherein:
the first line is composed of a blind through-hole,
a bonding pad is arranged for connecting the one of the surface acoustic wave filters and the blind through-hole, the bonding pad being arranged in the neighborhood of the blind through-hole, and
a first terminal for connecting the bonding pad and a second terminal to be connected to the common terminal.
In this embodiment, the length of the line connecting the terminal of the first surface acoustic wave filter or the transmitting surface acoustic wave filter which terminal is to be employed to connect it with the common electrode, and a diverging point located immediately below the blind through hole, at which diverging point the first line is branched, is made as short as the length of the blind through-hole. It is noted that a shorter distance between the signal transmitting terminal of the first surface acoustic wave filter or the transmitting surface acoustic wave filter and the diverging point at which the first line is branched, is effective to prevent the characteristics of a duplexer composed of the surface acoustic wave filter from deviating from the designated characteristics, because the shorter distance between the signal transmitting terminal of the transmitting surface acoustic wave filter and the diverging point at which the first line is branched, is effective to prohibit reflection of the signal which is being transmitted.
It is further noted that a blind through-hole is effective to improve the hermetic sealing quality.